Watching the familiar, rural landscapes of our youth give way to
suburban sameness has become as much a part of modern American life as
portable electronics, instant food, and wasted time in front of the
television. Nearly all of us have had the disappointing experience of
returning to what used to be the woods near our childhood homes and
finding a new subdivision. Or we have been shocked to see that some
corporate entity has erected aluminum-sided duplexes and an outlet mall
in the middle of our favorite vacation spot.

Like it or not, throughout this century, the United States has
undergone a steady process of urbanization as a larger and larger
percentage of the population has moved towards the cities. While
increasing urbanization may have some positive impacts on our
environment, such as the lower birth rates that come with a city
lifestyle, scientists are becoming more concerned about the negative
long-term effects. Unlike rural communities, urban sprawl completely
transforms the landscape and the soil and alters the surrounding
ecosystem and the climate.

Marc Imhoff, a biologist at NASAs Goddard Space Flight Center,
is one of these concerned scientists. For the past six years, he and a
team of researchers have been looking for ways to measure the effects of
urbanization on the biological productivity in the U. S. and other
countries around the world. They created a method of mapping
urbanization on a countrywide scale by using satellite images of the
light cities generate at night. With the resulting city lights maps,
they are now zeroing in on the impacts urban sprawl has on the food we
eat, the air we breathe, and the ecosystem within which we live.

Global city lights. The Eastern U.S., Europe, and
Japan are brightly lit by their cities, while the interiors of Africa, Asia, Australia, and South America
remain (for now) dark and lightly populated. (Data courtesy Marc Imhoff of NASA GSFC and Christopher Elvidge of
NOAA NGDC. Image by Craig Mayhew and Robert Simmon, NASA GSFC.)

High-resolution versions of this image are available on the Visible Earth